The price for the 2nd hand desktop you mentioned seems to be very reasonable, even borderline unbelievable, given the specifications you provided.
The Intel Core i7-5820K is a high-end processor known for its excellent performance. Although it's a few generations old, it's still a competent CPU for many tasks. The 32GB of RAM and m.2 SSD (256GB) and 4TB HDD represent a lot of memory and storage space which is beneficial for heavy workloads and storing a large amount of media or games.
The GTX 1050 Ti is a mid-range graphics card suitable for casual gaming and media production tasks. It's not the newest model, but it is still capable of running many graphics-intensive tasks smoothly. The Phanteks MATX case is a reputable brand known for its high-quality cases.
However, the price you mentioned is PHP 5K, which is roughly around $100. For all these components, even second-hand, this is an extremely low price. The average cost of a used PC with these specs would typically be much higher, even considering depreciation and wear and tear.
I would recommend double-checking the condition of the hardware. It's also a good idea to ensure there are no hidden issues like a faulty part or problems that might need significant repair. Sometimes, if a deal seems too good to be true, it might be. Always make sure to protect yourself when buying used hardware, whether that's through a secure payment method, a return policy, or buying from a trusted seller. Of course, if everything checks out, this is a fantastic deal!